package com.wuzao.chap6;


import java.util.List;
import java.util.Map;
import java.util.stream.IntStream;

import static java.util.stream.Collectors.partitioningBy;

public class PartitionPrimeNumbers {

    public static void main(String ... args) {
        System.out.println("Numbers partitioned in prime and non-prime: " + partitionPrimes(100));
//        System.out.println("Numbers partitioned in prime and non-prime: " + partitionPrimesWithCustomCollector(100));

    }

    public static Map<Boolean, List<Integer>> partitionPrimes(int n) {
        return IntStream.rangeClosed(2, n).boxed()
                .collect(partitioningBy(candidate -> isPrime(candidate)));
    }

    public static boolean isPrime(int candidate) {
        return IntStream.rangeClosed(2, candidate-1)
                .limit((long) Math.floor(Math.sqrt((double) candidate)) - 1)
                .noneMatch(i -> candidate % i == 0);
    }

//    public static Map<Boolean, List<Integer>> partitionPrimesWithCustomCollector(int n) {
//        return IntStream.rangeClosed(2, n).boxed().collect(new PrimeNumbersCollector());
//    }

//    public static boolean isPrime(List<Integer> primes, Integer candidate) {
//        double candidateRoot = Math.sqrt((double) candidate);
//        //return takeWhile(primes, i -> i <= candidateRoot).stream().noneMatch(i -> candidate % i == 0);
//        return primes.stream().takeWhile(i -> i <= candidateRoot).noneMatch(i -> candidate % i == 0);
//    }
/*
    public static <A> List<A> takeWhile(List<A> list, Predicate<A> p) {
        int i = 0;
        for (A item : list) {
            if (!p.test(item)) {
                return list.subList(0, i);
            }
            i++;
        }
        return list;
    }
*/
//    public static class PrimeNumbersCollector
//            implements Collector<Integer, Map<Boolean, List<Integer>>, Map<Boolean, List<Integer>>> {
//
//        @Override
//        public Supplier<Map<Boolean, List<Integer>>> supplier() {
//            return () -> new HashMap<Boolean, List<Integer>>() {{
//                put(true, new ArrayList<Integer>());
//                put(false, new ArrayList<Integer>());
//            }};
//        }
//
////        @Override
////        public BiConsumer<Map<Boolean, List<Integer>>, Integer> accumulator() {
////            return (Map<Boolean, List<Integer>> acc, Integer candidate) -> {
////                acc.get( isPrime( acc.get(true),
////                        candidate) )
////                        .add(candidate);
////            };
////        }
//
//        @Override
//        public BinaryOperator<Map<Boolean, List<Integer>>> combiner() {
//            return (Map<Boolean, List<Integer>> map1, Map<Boolean, List<Integer>> map2) -> {
//                map1.get(true).addAll(map2.get(true));
//                map1.get(false).addAll(map2.get(false));
//                return map1;
//            };
//        }
//
//        @Override
//        public Function<Map<Boolean, List<Integer>>, Map<Boolean, List<Integer>>> finisher() {
//            return i -> i;
//        }
//
//        @Override
//        public Set<Characteristics> characteristics() {
//            return Collections.unmodifiableSet(EnumSet.of(IDENTITY_FINISH));
//        }
//    }

//    public Map<Boolean, List<Integer>> partitionPrimesWithInlineCollector(int n) {
//        return Stream.iterate(2, i -> i + 1).limit(n)
//                .collect(
//                        () -> new HashMap<Boolean, List<Integer>>() {{
//                            put(true, new ArrayList<Integer>());
//                            put(false, new ArrayList<Integer>());
//                        }},
//                        (acc, candidate) -> {
//                            acc.get( isPrime(acc.get(true), candidate) )
//                                    .add(candidate);
//                        },
//                        (map1, map2) -> {
//                            map1.get(true).addAll(map2.get(true));
//                            map1.get(false).addAll(map2.get(false));
//                        });
//    }
}
